‘Google's 20% scheme has so far given birth to Gmail, Google Chrome and now Google Cardboard, its new virtual reality device.' Illustration: Ben Jennings

Sleep is overrated, according to Harriet Green, the departing chief executive of Thomas Cook, who famously survives on under four hours a night. The businesswoman is in the gym at 5.30am and at her desk shortly after 7; she spends the working week living in a hotel (instead of returning home to her husband and stepchildren) so she can fit more in. Somewhat ironically, Green can’t stay on the sun lounger for more than a few minutes on holiday without wanting to leap up and do something.

The results she achieves on this workaholic regime are little short of miraculous – the travel firm’s share price plummeted when she unexpectedly announced this week that she was quitting – so it’s odd that she is leaving abruptly after only two years. Could it be that corporate Britain is no longer quite as comfortable with the lunch-is-for-wimps culture as it was?

One in 10 Britons would like to work fewer hours (and take a pay cut to do so), according to a new Office for National Statistics survey – roughly the same as would like to do more but can’t find a full-time job. Working hours in Britain have actually risen slightly overall since the crash, despite the boom in low-paid part-time work, as full-timers spend longer at their desks – either from fear or necessity, as vacancies go unfilled and those left are expected to pick up the slack.

Even the French are now debating whether to ditch their cherished 35-hour working week, because in practice too few people are sticking to it. The world is polarising between those with more work than they want and those with not enough.

Of the two, being overworked obviously looks the better gig, since at least you’re statistically more likely to be well-paid and doing interesting, stimulating things. (But one feels for Green’s hairdresser, who apparently reaches her house before 7am to do her daily blowdry.)

But long hours are associated with a greater risk of heart disease, stroke and even diabetes; and the evidence suggests that if anything, lack of sleep is underrated, linked as it has been to everything from obesity to premature mortality. Pilots crash, surgeons slip, and politicians lose perspective when they’re tired, while staying up all night to finish the job leads as often to knackered incoherence as it does to success.

All of which means that while the rise of low-paid underemployment is obviously alarming, overwork is more than just some self-indulgent rich man’s problem, on a par with discovering that your new Rolls-Royce doesn’t fit in the garage.

What’s striking is that the group most anxious to work less were over 50, and that so many of them clustered in predominantly male-dominated professions: chief executives, senior police and army officers. This isn’t just about mothers longing to spend more time with small children but about burnt-out men trapped in careers where “part-time” sounds like a professional death wish, or in circumstances that don’t allow for a pay cut. In surveys it’s men, not women, who now express greatest dissatisfaction with their work-life balance. The good news for the overworked, dreaming forlornly of doing 11 fewer hours a week on average, is that even when a four-day week isn’t feasible, we could be far more imaginative about the fifth.

Friday is the easiest morning to find a seat on my local commuter train for a reason: working from home is growing in popularity, and the best day for it is just before the weekend. If that means people starting early, long before they’d normally reach their desks, and finishing early – well, so what? Better than sitting around in the notorious dead zone that is most offices after 3pm on a Friday, convincing yourself that it’s too late now to finish this before the weekend and, oh well, it could wait until Monday; better than furtively Facebooking while pretending to work, while everyone slopes off to the pub (“leaving early to beat the traffic”).

So endemic is the Friday afternoon skive that some companies now cut their losses by sending staff home early in the slack days of summer. The fashion retailer Asos has “doss Fridays”, on which staff can leave at 3pm, as do several major publishing companies: Kellogg’s has for years given Friday afternoons off as a perk after finding that cutting out the dead time actually boosted productivity overall.

Working longer, in other words, only guarantees achieving more if you’re confident that every minute is well spent. This week, on the way back from a work event (at around 10pm) I listened on the car radio to a fascinating interview with the concert pianist Janina Fialkowska, explaining how cancer surgery on her arm had left her unable to manage her normal six to seven hours’ practice a day. Yet surprisingly, music critics thought her playing had, if anything, improved. She reckons she gets more now from three hours of highly concentrated, focused practice than from her previous marathon sessions.

Not everyone, of course, has the flexibility of a concert pianist. But there are other ways to capitalise on the Friday feeling than simply slacking off. Google’s “20% time” project, where selected engineers get the equivalent of a day a week to play around with their own ideas on the company’s time, may sound like one of those pointlessly adolescent things tech companies do, like installing a slide at headquarters that nobody with a modicum of self-respect actually uses. But the scheme has so far given birth to Gmail, Google Chrome and now Google Cardboard, its new virtual reality device.

It doesn’t matter if nine in 10 of the projects turn out to be dead ends if the 10th is the game changer that would never have happened otherwise. The company is well aware that people are likely to work harder on a pet project they enjoy than on one dumped on them from on high, and that creativity requires occasional freedom from the treadmill.

Indeed, given the need for imaginative solutions to rising demand and shrinking budgets in public services, one wonders whether carving out a few hours a week for NHS consultants or chief constables to clear the diary and actually think might not pay dividends too. Free our Fridays, in other words, and you might be pleasantly surprised at what’s achieved by Thursday night. Happy weekend.